1. Field of the Invention
The present invention relates to an apparatus and method of controlling switch units, and in particular, to an apparatus and method of controlling switch units installed between a battery pack and a load, and a battery pack and a battery management system comprising said control apparatus.
2. Description of the Related Art
Vehicles using fossil fuel, such as gasoline, diesel and so on, generate a lot of harmful exhaust gases and pollute the air. The harmful exhaust gas is one of factors affecting global warming and exerts an injurious effect upon global environment. To solve this problem, attempts have been made to develop vehicles reducing fossil fuel consumption or running on alternative fuel. And, recently, interests are centered on HEV (Hybrid Electrical Vehicle) or EV (Electrical Vehicle) capable of running on an electrical energy supplied from a high-capacity battery pack.
HEV can run by an engine consuming fossil fuel and a motor driven by an electrical energy supplied from a battery pack. HEV includes HCU (Hybrid Control Unit). At the time of applying the brake or reducing the speed of HEV, a power mode is converted to a generation mode under the control of the HCU. Then, the battery pack is charged with an electrical energy output from a generator connected with the engine under the control of BMS (Battery Management System) connected with the HCU. In a power mode, the electric current is supplied from the battery pack to the motor and the motor drives the vehicle.
The battery pack and the motor corresponding to a load are connected with each other through a relay switch unit. In turn, the connection between the battery pack and the load is released by controlling the relay switch unit.
FIG. 1 is a circuit diagram conceptually illustrating a connection of a battery pack and a load through a relay switch unit.
Referring to FIG. 1, a relay switch control method according to the conventional art is described as mentioned below.
To connect a battery pack 10 with a load 40, first a (−) side relay switch unit 30 is turned on. Next, a free charge switch unit 22 is turned on, so that electric current, of which a magnitude level is limited by a current limiting resistor (R) connected in series with the free charge switch unit 22, is applied to the load 40. Under this condition, after a predetermined time passes, a (+) side relay switch unit 20 is turned on and the free charge switch unit 22 is turned off. In this way, the battery pack 10 and the load 40 are connected with each other.
Here, the use of the free charge switch unit 22 in connecting the battery pack 10 with the load 40 prevents in-rush current from being applied to the load 40 when connecting the battery pack 10 with the load 40.
On the contrary, the connection between the battery pack 10 and the load 40 is released by turning off the (+) and (−) side relay switch units 20 and 30 in a preset order.
When the relay switch unit is turned off, arc generates at a contact of the relay switch unit due to the relay's inductance component. The generated arc damages the contact of the relay switch unit, and consequently, reduces the using period of the relay switch unit.
According to the conventional relay switch control method, a manipulation order of the relay switch unit is preset, and consequently, damage caused by arc is relatively concentrated on any one relay switch unit. As a result, it increases the frequency of breakdown and malfunction occurring to any one of two relay switch units and reduces the switch unit replacement cycle.